A sensor device can be placed on the upper-body of a user (e.g. chest area) to sense an electrocardiogram (ECG) signal through electrodes that are attached to the skin of the user. The ECG signal is used to measure a variety of health related features of the users including the user's heart rate. The sensor device can also detect the user's motions through an embedded microelectromechanical systems (MEMS) sensor. The data detected from the MEMS sensor is used to measure the user's activity level.
Conventional devices measure heart rate alone to assess the user's health without the context of the user's activity level. For example, a high heart rate (120+ beats per minute or bpm) could signal a cardiovascular condition during rest but is normal during exercise. A low heart rate (<60 bpm) could signal a cardiovascular condition if detected during strenuous exercise but is normal during rest. However, conventional devices are not aware of the user's activity when making heart rate measurements. Therefore, there is a strong need for a cost-effective solution that overcomes the above issues. The present invention addresses such a need.